Effect of Rhodopseudomonas palustris G5 on seedling growth and some physiological and biochemical characteristics of cucumber under cadmium stress

At present, we investigated whether Rhodopseudomonas palustris G5 strain treatments diminished the damage on cucumber seedlings caused by cadmium (Cd) stress. Growth and physiological parameters of cucumber seedlings were determinated at laboratory after co-treating seedlings with Rhodopseudomonas palustris G5 strain and different concentrations of Cd (50, 100, 150, 200, 300 mg L-1), The results indicated that Cd stress significantly reduced shoot height, root length, total chlorophyll content, root activity, but increased malondialdehyde (MDA) content. In addition, lower concentrations of Cd stress increased soluble sugar and soluble protein contents, and improved the activities of superoxide dismutase (SOD; EC: 1.15.1.1) and peroxidase (POD; EC: 1.11.1.7), but higher concentrations of Cd decreased the soluble sugar and soluble protein contents, and inhibited SOD and POD activities. G5 strain application markedly reduced the toxic effects of Cd on cucumber seedlings. In sum, G5 strain treatment significantly alleviated damage on cucumber seedlings caused by Cd, and increased shoot height, root length, total chlorophyll content, root activity, the contents of soluble sugar and soluble protein, as well as the activities of SOD and POD, but decreased MDA content compared with non-treating plants.